The typical asking rate per listing is in the $10's per square foot per year. The Excelsior region is going through a a rise in rates. In the last 3 months, the median rate rose $18 per sqft per year.
In the last 90 days, 5 listings have been made available, which means office spaces most likley are going fast. You'll want to be prepared to make an offer immediately. About 40% of the available leases in the Excelsior are subleases, so you might be able to sign a shorter term by taking over a previous lease. There aren't many listings below 2,000 square feet posted, so finding a space for a small business might be tough.
The standard measurement for office space in this area is around 1,290 sqft. Most properties in this region are close to 2 stories. Most buildings in this market were built in 1985 and are Class A.